Energy parameters assessment, under scale effect calculation of centrifugal fans with radial blades

Abstract

The centrifugal fans with radial blades are used in various industrial energy systems, associated with high dustiness, due to their self-cleaning ability and their reliable operation. Radial fans are used in cement, asphalt industries and various dust collection facilities. The uniqueness of the different working environment and the specifics of each system require the use of a fan, designed for the particular application. Due to the dimensions of the machines, before the fan is produced, it normally goes through model tests. In model studies of rotodynamic fluid machines, differences are sought between the expected parameters from the application of the similarity theory and the obtained energy parameters. These differences are commonly referred to as the scale effect. Estimating the scale effect in model tests leads to the use of energy efficient machines for a given system. These are the one, that give the desired system parameters when operating in the region of maximum efficiency. Thus, the purpose of modeling is to transfer the efficiency obtained for a given mode of operation of the model machine to the prototype. The operation in the optimal mode of the prototype fan leads to energy savings and a reduction in energy costs for a given technological system. In the presented paper are evaluated the differences between expected and obtained parameters that help to realize a model for a centrifugal fan with radial blades. The results of model tests, conducted on two geometrically similar centrifugal fans with radial blades, where the inlet and outlet angles of the impeller are the same (β1=β2=900 ), are given. The fan impellers are semi-open type with 12 blades. Each of the impellers is tested in a geometrically similar helical chamber. Model tests have been conducted on a laboratory test-bench, meeting the requirements of AMCA 210 or ISO5801. The test-bench is equipped with the complete measuring equipment, according to the standards used. During the model tests, both the energy parameters of the fans and the parameters of the surrounding environment are measured. The results of the energy tests of the fans are given in the paper, as well as the coefficients concerning the scale effect are determined and analyzed.